A cement truck has jackknifed on Highway 41 West just inside the Atascadero city limit, according to the CHP Web site.
The first call reporting the incident came in at 9:10 a.m. The truck's brakes may have locked up, according to the site. It is located in some curves and may be blocking lanes near Los Altos Road.
A big-rig tow truck has been called to the scene.